CT-Pathology Correlations

Case 22

Section 1

Look at images 1, 2, and 3.

Image 1

What are the abnormalities?

Answer

Image 2

Image 3

This image confirms a basilar predominance of the disease.

Section 2

Image 1

In the left lung find an example of traction bronchiectasis.

In the left lung find an example of confluent ground-glass opacity with consolidation and reticular change.

Image 2

In the right lung find 2 examples of traction bronchiectasis/bronchiolectasis.

In the right lung find an example of reticular change.

Section 3: Histologic Findings

Extensive filling of many alveoli with macrophages is present throughout the lobule. Alveolar walls are only slightly thickened by collagen, a few chronic inflammatory cells, and occasional lymphoid aggregates. Type II cell hyperplasia is present. More fibrosis may occur with time.

Find a respiratory bronchiole.

Find 2 alveolar walls with slight fibrosis and inflammation.

Find a lymphoid aggregate.

Find and outline 3 nests of alveolar macrophages.

Find an example of type II cell hyperplasia.

The cytoplasm of the macrophages often has light brown pigment, which can be distinguished from iron by a negative or weakly positive iron stain.

Differential diagnosis of ground-glass opacity, consolidation, and reticular change on HRCT: Non-specific interstitial pneumonia, desquamative interstitial pneumonia, acute interstitial pneumonia, bronchiolitis obliterans organizing pneumonia, chronic eosinophilic pneumonia, and Churg-Strauss syndrome. This degree of ground-glass opacity with some consolidation can be seen with usual interstitial pneumonia, but is atypical.

Diagnosis: Desquamative interstitial pneumonia (DIP)

Histologic differential diagnosis: Desquamative interstitial pneumonia and respiratory bronchiolitis interstitial lung disease (RBILD). When the alveolar macrophages and interstitial thickening are present diffusely throughout the lobule, DIP is diagnosed. When the inflammation is confined to the region of the respiratory bronchiole, the term RBILD is used. The two entities (DIP and RBILD), both closely associated with smoking, may be different ends of a spectrum clinically, as well as histologically. A focal DIP-like reaction may be found in asbestosis and Langerhans' cell histiocytosis. Pulmonary hemorrhage syndromes should be excluded with an iron stain.

Diagnostic features of desquamative interstitial pneumonia on HRCT [1]

Peripheral predominance of ground-glass opacity, mid and lower lung > upper lung
Reticular change
Traction bronchiectasis
Focal lung sparing

Reference

1. Hartman T, Primack S, Swensen S, Hansell D, McGuinness G, Müller N. Desquamative interstitial pneumonia: thin-section CT findings in 22 patients. Radiology 1993; 187:787-790.

2. Katzenstein A, Myers J. Idiopathic pulmonary fibrosis. Clinical relevance of pathologic classification. Am J Respir Crit Care Med 1998; 157:1301-1315.

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